While the principles of this invention apply to the automated closing of sliding window or door panel members in general, it is particularly applicable to the closing of sliding screen doors. Therefore, in order to simplify the following discussion, the invention will be described with respect to its applicability to sliding window or door panels of the screen type. The screen member of a sliding door is generally operable to obstruct the door opening when the sliding glass portion of the door is "open," and is slidable in or between oppositely disposed upper and lower tracks in a direction parallel to and in close proximity with the glass door panel so as to leave the access portion of the door opening unobstructed when slid entirely to its "open" position. There are numerous occasions wherein it is desirable for the movable screen door portion to "automatically" return to its closed position following the entrance or exit of a person or animal through the door opening. For example, it may be desirable to immediately close the door panel in order to keep animals or small children on one side of the screen panel, while maintaining insects and the like on the other side. Further, it may be desirable for a person carrying an object or objects to open and pass through the sliding screen door, without being required to put down the objects or being required to balance such objects while working free a hand in order to close the screen panel behind him/her.
Many attempts have been made over the years to provide an acceptable closure mechanism for slidably movable screen panels for gliding windows or sliding doors, often referred to as patio doors. While the principles of operation are generally the same for window and door screens, the closure of door screens is much more difficult due to their size and frequency of use. Previous attempts have generally fallen short of simultaneously providing the most desired features for such a closure apparatus, namely: simplicity; ease of manufacture, use and installation; ability to retrofit to existing installed structures; low cost; smooth and efficient operation; versatility and adaptability to variously sized window or door panels; pleasing aesthetics; uniform and properly tensioned closure force; adjustable closure tension; and above all--high reliability over the operative life of the movable panel.
Prior attempts at sliding panel closure apparatus have generally proved to be cumbersome or have required uniquely designed window or door frame configurations, and/or have exhibited low reliability and fairly short operative life. For example, the device illustrated in U.S. Pat. No. 4,301,623 requires a sliding door panel to have a specially designed frame portion for enclosing the tension spring closure apparatus. A similar closure assembly, configured to be housed within the building wall structure or configured as a cumbersome elongated device attached to the movable screen member, is illustrated in U.S. Pat. No. 4,003,102. Yet another bulky and unsightly closure mechanism which uses a complicated block and tackle pulley arrangement is illustrated in U.S. Pat. No. 4,819,295. Such configurations generally do not satisfy the desired simplicity, pleasing aesthetics or low-cost requirements for such closure apparatus.
Besides the need for an aesthetically pleasing closure housing which is easy to attach and retrofit to an existing door or window structure, such closure mechanism should be operable in a manner so as not to obstruct the door or window passageway when the door or window is positioned in an "open" position. A closure apparatus such as disclosed in U.S. Pat. No. 4,675,938 places the closure device and its associated cable assembly near the top of the door but partially obstructs the door passageway in an unsightly and potentially dangerous manner. Other closure configurations such as illustrated in U.S. Pat. No. 5,131,188 enclose the closure mechanism within the upper frame assembly of the door or within a detent portion of the screen door frame. Such closure structures which apply closure pressure to either the top or the bottom of the sliding door member are generally ineffective and make the screen panel susceptible to binding due to the tendency of the panel to tilt or cock between the frame tracks during operation.
Many prior door closure members have utilized some type of a spring assembly for providing the necessary closure force to the slidable panel. One type of spring has been the simple coiled tension spring, which in order to be operatively effective over the entire door movement distance, requires significant longitudinal length and is difficult to conceal or house for retrofit applications. Others have used spring configurations referred to as constant force springs, which have proven to have low reliability and high susceptibility to breakage over extended periods of use.
The present invention addresses the above shortcomings of prior window or door closure structures. This invention uses a unique spring configuration and combines the best features of prior closure structures to simultaneously provide a highly reliable, aesthetically pleasing, simple, low-cost, easy to use and install, adjustable tension, and universally applicable automatic movable panel closure member which provides generally uniform pressure to the movable panel member throughout its entire closure movement and which consistently enables the movable panel to close in a smooth and uniform manner over the operative life of the panel.